Comparison

Stone Crushing Machine Motors required high starting torque at the time of starting the motor. It is not required all the time this motors are the short time duty cycle, so Soft starter only limit the starting current to motor. The torque Compensation or the Torque Boosting function is absent in the Soft Starter.

Although both devices falls under reduced voltage starting method, but soft starter can not vary the frequency. Soft starter just helps to lower the starting current and smoother the start up. Whereas AC drive inverter its much more intelligent and it has all the functions of soft starter. If the money is not an issue and proper investigation of application, I will consider AC drive inverter instead Soft starter.

The difference is the soft starter is primarily a mechanical soft start. You reduce the voltage and limit the current to ease the mechanical stresses associated with motor starting. You do have the potential to reduce the current associated with starting, but this benefit is highly dependent on many variable and can change dependent on the particular voltage condition at the time of starting. Medium Voltage Motors do not have the generous amounts of starting torque many people take for granted with 460v motors.

The advantages/disadvantages of different types of motor starters like DOL, star/ delta, korndorfer, primary resistance/reactance, shunt capacitance, slip ring, vfd, vsd, auto transformer etc.DOL (simple start up but reflect to high voltage drop, high starting current, low starting period duration)less power saving.star/delta decrease the starting current to 1/3 but required many relays for control change between start connection then to delta.